The present invention relates to a wiring harness plug, especially a planar two-cell limiting current probe, including a housing made of a base element and a cover element, as well as a sensor unit and an adjusting element connected to the sensor unit.
Wiring harness plugs of the above kind are, as a rule, developed as lambda probes, the terminals provided in the wiring harness plug being provided for adjustment, signaling and heating of the probe. Lambda probes and lambda closed loop A/F control, these days, represent an effective exhaust gas cleaning method in conjunction with a three-way catalyst. The lambda probe, which is, for example, screwed into an exhaust gas system, includes a measuring sensor for determining the oxygen content in the exhaust gas.
Residual oxygen content is very suitable as a measured variable, and regulates the air/fuel ratio, since it indicates precisely whether the air/fuel mixture is combusting completely.
In this regard, the lambda probe delivers a voltage signal which represents the momentary value of the mixture""s composition and follows the changes in the mixture. Fuel supply to the engine is regulated, corresponding to the signal of the lambda probe, by a carburetion device in such a way that a stoichiometric air/fuel ratio lambda=1 is reached. Heated or unheated probes are installed, depending on the construction of the exhaust gas system and the installation conditions. Lambda probes find further application outside motor fuel vehicles, for instance, for regulating gas engines or oil/gas burners.
In particular, broad-band lambda probes are constructed in a modular way, and permit the integration of several functions, in connection with planar technique. As a rule, they have functional layers made of a porous protective layer, an outer electrode, a sensor foil, an inner electrode, a reference air channel foil, an insulating layer, a heater, a heating foil and terminal contacts.
Since the broad-band lambda probe includes the combination of a Nernst concentration cell (=sensor cell) with an oxygen ion-transporting pump cell, it can measure very accurately not only at the stoichiometric point where lambda=1, but also in the lean and the rich range.
Each probe has to be adjusted individually. For this, the probe has a built-in resistor (xe2x80x9cmini-hybridxe2x80x9d). The adjustment, which is preferably made with the aid of a laser beam, is done in such a way that the resistor layer, which is on a ceramic substrate, is correspondingly removed, whereby a change in resistance is brought on, resulting in an adjustment.
Up to now, the adjustment has taken place in that the housing of the wiring harness plug, in which the resistor is built in, is brought to the adjustment location without the cover element. After the appropriate laser treatment for the adjustment, the cover element is then slipped on.
The cover element has additional seals, in order to prevent humidity, dirt or the like from penetrating the wiring harness plug.
One disadvantage of the design of the wiring harness plug described above is that additional working and installation steps are required in order to close the wiring harness plug appropriately for its function after the adjustment. Additionally an additional cover element is separately manufactured together with a seal, and this element is made available in the adjustment region.
An object of the present invention is to further develop a specific embodiment of a wiring harness plug having hybrid electronics so that it is adjustable in a simple manner.
The object is attained in that the cover element is undetachably positioned on the housing, and that the cover element is transparent, so that a laser beam can penetrate the cover element and processing of the adjustment element can take place.
An advantage of the present invention is that the cover element is already mounted on the wiring harness plug before the adjustment. Preferably, the cover element is positioned directly and undetachably on the housing, such as being extruded on the housing. This makes it no longer necessary to produce an additional component, and to make it available at the location of the adjustment, and mounting it.
This also does away with seals liable to aging, which have been used to seal the cover element from the housing in designs up to now.
Preferably elements are provided in the housing, into which individual parts of the probe can be installed. These elements are preferably developed as clamping elements.
A further specific embodiment of the present invention is developing the cover element and the base body in one piece.
Further advantageous refinements of the present invention come to light from the following description, the claims, as well as the drawings.